eaps 53600: introduction to general circulation of the ...dchavas/download/...semester project you:...
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EAPS 53600: Introduction to General Circulation of the AtmosphereSpring 2020Prof. Dan Chavas
Source: https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=30017
NASA GEOS-5 Computer Model
Source: https://www.youtube.com/watch?v=R2lP146KA5A
What’s wrong with this animation?
Topic: Climate context for atmospheric circulationsReading:1. (Review of basics: Hartmann Ch 1.1-1.7, 3.1-3.2)2. Hartmann Ch 2, 3.8, 3.10-3.11
Introduce yourself: Name + year + research interest / majorIf you have a preferred name that differs from the official Purdue listing, please let me know!
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Purdue is committed to creating and sustaining a welcoming campus for all.
Does everyone have a laptop?
Who has experience with MATLAB?Python?
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Course objectives (briefly)
1. Physics of the range of large-scale atmospheric circulations found on Earth
2. Hypothesis-driven inquiry using labs, models, and data
Large-scale circulations1) Movement of air2) Over long horizontal
distances (L>100 km)
Student-driven (you)
Hypothesis-driven
Student-driven (you)
Hypothesis-driven
An example, right off the bat
𝒈 =𝑮𝒎𝒓𝟐
This is an equation for the gravitational acceleration at some radius 𝑟induced by an object of mass 𝑚:
Standard lecture
[𝑚𝑠+,]
“I’m wondering... would a ball hit the ground faster on the Earth or the Moon?”
Hypothesis-driven
A testable hypothesis: A ball dropped from the same height would hit the ground faster on the Earth than the moon.
Group:1) What do you need to know to test this hypothesis?2) How could you test this hypothesis?
Direct observation vs. Laboratory (i.e. physical) simulation vs. Model simulation (equations/computer)
Semester project
You:• Propose a testable hypothesis – anything related to large-scale circulations• Propose methodology for testing – could use data, computational model, laboratory (rotating tank)• Execute• Synthesize in oral presentation (last day of class) + final paper (due during finals week)
Projects are individual; undergrads can work in a pair if desired.
Milestones are on the course schedule.• First milestone (M1a) due week of 01/27: three hypotheses of interest + methods to test (as
specific as possible) • You will review each others milestones!
Please bring your books to class!
You will be able to use figures / equations / your notes from the reading in group discussion.
Other questions?
Climate context for atmospheric circulations
What’s wrong with this animation?
https://media.giphy.com/media/o2XbUUi1CXKTe/giphy.gif
Planetary dynamicalforcing:1) rotation (𝑓);2) differential rotation (𝑓varies with latitude)
𝑓 = 0
𝑓 = 2Ω
Planetary thermodynamicforcing: differential heating(solar insolation gradients, surface variability (land))
𝑓 = 2Ω𝑠𝑖𝑛𝜙
These simple external ingredients...
Source: https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=30017
NASA GEOS-5 Computer Model
35021885
White: total precipitable water (brigher white = more water vapor in column)Colors: precipitation rate (0 − 1588
9:, red=highest)
Kelvin waves, Rossby waves
Rossby waves / Extratropical cyclones
Tropical cyclones
Hadley cellWalker cell
Monsoon
Madden-Julian Oscillation (MJO)
... generate many types of horizontal circulations!
A couple of contrasts to think about
1) Tropics (weakly-rotating) vs. extra-tropics (strongly-rotating)
2) Waves vs. overturning circulations• Waves (gravity, Rossby…): require a dynamical restoring force• Overturning circulations (Hadley, Walker...): principally a response to differential heating
(less dense fluids tend to rise...)
You will investigate this with the rotating tank!
Student-driven (you)
Hypothesis-driven
Question: would our atmosphere be different if air didn’t move?
This is Homework 1 (posted on blackboard): due next Thursday 01/16.You will start today in class – groups of 3.
Hypothesis: If air didn’t move, the equator-pole surface temperature gradient would be larger than it is on the real, present-day Earth.
One specific, testable hypothesis
Test this hypothesis using Hartmann Ch 2-3.
Group (10 min):1) What information do you need to test this hypothesis?2) What methods could you use to obtain that information?
Hypothesis: If air didn’t move, the equator-pole surface temperature gradient would be larger than it is on the real, present-day Earth.
Options:1. Direct observation2. Laboratory (i.e. physical) simulation3. Model simulation ß only option... how could you do it?
What assumptions would you make?
An experimental tool: a model for a single column of surface + atmosphere in radiative equilibrium http://singh.sci.monash.edu/Nlayer.shtml
Group (10 min each):1) What experiments would you propose with this model to test this hypothesis?2) What assumptions will you be making in your methodology?
This model finds the solution with 1 or more atmospheric layers, and each layer is 1) transparent to shortwave radiation (i.e. shortwave emissivity = 0), and 2) can have a longwave emissivity 𝜖 ≤ 1.
see Hartmann Ch 2.5, 3.8
A second experimental tool: a model for a single column of surface + atmosphere in radiative-convective equilibrium: http://rcmodel.mit.edu/
see Hartmann Ch 3.10
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